Fluid - Sudden splashes during calm down
Id say rerun the bake. Fluid Dynamics are very complicated and your computer probably had some sort of Error which reslulted in a sudden net plus of Energy, thus creating the splash.
Another option may be resonance. See, the Fluid still has a lot of energy even if it is close to a resting state. And as all Dynamic systems tend to do, the Fluid kind of equalizes itself by moving. And so what can happen is that a lot of Energy suddenly gets released because a lot of Particels just happen to hit the right frequency. There is something similar that happens in the real world, but that is related to Quantum Mechanics. And Blender dosnt take those effects into account as far as i know.